IThe long-term scientific aim of this project is to develop an ultrawideband (UWB) space-time microwave imaging method for early-stage breast cancer detection. The combination of robust space-time signal processing techniques and low-power UWB microwave radar techniques offers the promise of a highly sensitive breast cancer screening tool. UWB sensing systems take advantage of the features of both lower and higher frequencies, thereby providing sufficient penetration into Iossy biological tissue and spatial (and temporal) resolution. Furthermore, super-resolution - that is, imaging resolution that overcomes the classical diffraction limit - can be achieved with UWB signals in conjunction with array-based transmitters and receivers. The goal of the proposed work is to bring about fundamental advances in UWB microwave based detection, classification, monitoring, and imaging techniques, including the design and implementation of a pre-clinical prototype imaging system and the evaluation of this novel approach using anthropomorphic breast phantoms that mimic the configuration of the patient in the clinical setting. The research will culminate with in vivo imaging studies on human research subjects. The following technical aims will be pursued to accomplish this goal: 1) To develop advanced space-time signal-processing algorithms that can be applied to UWB microwave scattered signals for the 3-D detection, imaging, classification, and monitoring of malignant breast lesions. 2) To characterize and refine the performance of our UWB imaging techniques using anatomically realistic numerical breast models and anthropomorphic physical breast tissue phantoms in conjunction with our first-and second-generation hardware prototype systems. 3) To construct a second-generation, pre-clinical prototype system suitable for in vivo imaging studies. 4) To conduct initial in vivo imaging studies with human research subjects using the pre-clinical prototype system. Successful completion of these aims will provide compelling evidence of efficacy, permit subsequent development of a microwave breast imaging system suitable for clinical trials, and lead to the establishment of low-power UWB microwave imaging as a clinically relevant non-ionizing, non-invasive tool for breast cancer detection/screening and monitoring. The predicted safety, comfort (no breast compression), ease-of-use and low-cost features should improve public compliance with annual screening recommendations.